Adding a macro to define the vlog module in use adds a level of
indirection, which makes it easier to change how the vlog module must be
defined. A followup commit needs to do that, so getting these widespread
changes out of the way first should make that commit easier to review.
Waiting for a lockfile can cause mysterious pauses for users. Logging a
warning to the console every so often gives them feedback on what is
happening.
Reported-by: Justin Pettit <jpettit@nicira.com>
